/*
 * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package org.eclipse.imagen.media.codec;

import java.awt.image.Raster;
import java.awt.image.RenderedImage;
import java.io.IOException;
import java.io.InputStream;

/**
 * A partial implementation of the <code>ImageDecoder</code> interface useful for subclassing.
 *
 * <p><b> This class is not a committed part of the JAI API. It may be removed or changed in future releases of JAI.</b>
 */
public abstract class ImageDecoderImpl implements ImageDecoder {

    /** The <code>SeekableStream</code> associcted with this <code>ImageEncoder</code>. */
    protected SeekableStream input;

    /** The <code>ImageDecodeParam</code> object associated with this <code>ImageEncoder</code>. */
    protected ImageDecodeParam param;

    /**
     * Constructs an <code>ImageDecoderImpl</code> with a given <code>SeekableStream</code> and <code>ImageDecodeParam
     * </code> instance.
     */
    public ImageDecoderImpl(SeekableStream input, ImageDecodeParam param) {
        this.input = input;
        this.param = param;
    }

    /**
     * Constructs an <code>ImageDecoderImpl</code> with a given <code>InputStream</code> and <code>ImageDecodeParam
     * </code> instance. The <code>input</code> parameter will be used to construct a <code>ForwardSeekableStream</code>
     * ; if the ability to seek backwards is required, the caller should construct an instance of <code>SeekableStream
     * </code> and make use of the other contructor.
     */
    public ImageDecoderImpl(InputStream input, ImageDecodeParam param) {
        this.input = new ForwardSeekableStream(input);
        this.param = param;
    }

    /**
     * Returns the current parameters as an instance of the <code>ImageDecodeParam</code> interface. Concrete
     * implementations of this interface will return corresponding concrete implementations of the <code>
     * ImageDecodeParam</code> interface. For example, a <code>JPEGImageDecoder</code> will return an instance of <code>
     * JPEGDecodeParam</code>.
     */
    public ImageDecodeParam getParam() {
        return param;
    }

    /**
     * Sets the current parameters to an instance of the <code>ImageDecodeParam</code> interface. Concrete
     * implementations of <code>ImageDecoder</code> may throw a <code>RuntimeException</code> if the <code>param</code>
     * argument is not an instance of the appropriate subclass or subinterface. For example, a <code>JPEGImageDecoder
     * </code> will expect <code>param</code> to be an instance of <code>JPEGDecodeParam</code>.
     */
    public void setParam(ImageDecodeParam param) {
        this.param = param;
    }

    /** Returns the <code>SeekableStream</code> associated with this <code>ImageDecoder</code>. */
    public SeekableStream getInputStream() {
        return input;
    }

    /**
     * Returns the number of pages present in the current stream. By default, the return value is 1. Subclasses that
     * deal with multi-page formats should override this method.
     */
    public int getNumPages() throws IOException {
        return 1;
    }

    /**
     * Returns a <code>Raster</code> that contains the decoded contents of the <code>SeekableStream</code> associated
     * with this <code>ImageDecoder</code>. Only the first page of a multi-page image is decoded.
     */
    public Raster decodeAsRaster() throws IOException {
        return decodeAsRaster(0);
    }

    /**
     * Returns a <code>Raster</code> that contains the decoded contents of the <code>SeekableStream</code> associated
     * with this <code>ImageDecoder</code>. The given page of a multi-page image is decoded. If the page does not exist,
     * an IOException will be thrown. Page numbering begins at zero.
     *
     * @param page The page to be decoded.
     */
    public Raster decodeAsRaster(int page) throws IOException {
        RenderedImage im = decodeAsRenderedImage(page);
        return im.getData();
    }

    /**
     * Returns a <code>RenderedImage</code> that contains the decoded contents of the <code>SeekableStream</code>
     * associated with this <code>ImageDecoder</code>. Only the first page of a multi-page image is decoded.
     */
    public RenderedImage decodeAsRenderedImage() throws IOException {
        return decodeAsRenderedImage(0);
    }

    /**
     * Returns a <code>RenderedImage</code> that contains the decoded contents of the <code>SeekableStream</code>
     * associated with this <code>ImageDecoder</code>. The given page of a multi-page image is decoded. If the page does
     * not exist, an IOException will be thrown. Page numbering begins at zero.
     *
     * @param page The page to be decoded.
     */
    public abstract RenderedImage decodeAsRenderedImage(int page) throws IOException;
}
